The present invention generally relates to cooking of food products and, more particularly, to an improved method and apparatus for precooking of food product slices in a continuous stream of cooking oil upstream of a conventional fryer.
Potato chips were originally prepared on a batch basis. Hand cut potato slices were immersed in a kettle of hot cooking oil and cooked until they achieved a desired appearance. The chips were then removed from the cooking oil and allowed to drain.
With the increased popularity of potato chips and the commensurate increase in demand for this product, processes and equipment were developed to prepare potato chips on a continuous basis and thereby increase production volumes. Typically, in the continuous production of potato chips, raw potatoes are first peeled and sliced. Next, the resulting slices are washed, usually with water, to remove the starch which is released during the slicing process and coats the potato slices. The washed slices are then dropped into a fryer containing a continuous stream of heated cooking oil at a temperature of approximately 325 to 375 degrees F. In the ensuing cooking process moisture is released from the slices and replaced to some extent by the cooking oil. The final product will have an oil content of approximately 35% to 5% by weight and a moisture content of approximately 1.5% to 2.2% by weight.
Demand for potato chips continues to increase and is met for the most part by chips prepared on a continuous basis. However, more recently there has also been an increased demand for so-called "kettle cooked" chips which have the appearance and flavor of chips cooked by the old-fashioned batch process. However, the same problem exists today with respect to batch-prepared potato chips that existed at the original introduction of potato chips. That is, batch production is slow, which results in both an increased price for the batch-prepared product and insufficient volume to meet demand.
Recently a method and apparatus for carrying out the method have been developed for addressing the demand for "kettle cooked" chips. The method and apparatus, as disclosed in the patent application cross-referenced above, produce on a continuous, high volume basis potato chips having an appearance, texture and flavor heretofore found in chips prepared on a batch basis. This is achieved by introducing and precooking unwashed potato slices for about several seconds in a sluice containing a continuous stream of cooking oil heated to a temperature of approximately 200 to 300 degrees F. Thereafter, the precooked slices are cooked or fried for about 5 to 10 minutes in a conventional fryer containing a continuous stream of cooking oil maintained at a temperature of approximately 300 to 400 degrees.
In this method, the layer of natural starch coating or enveloping the freshly sliced potatoes is caramelized in the precooking step to form a barrier which resists the penetration of cooking oil in the subsequent cooking or frying step. The resulting potato chip has a lower oil content, approximately 28% to 35% by weight, than chips cooked in a conventional manner e.g 35% to 45% by weight. Additionally, the caramelized starch coating on the slices tends to retard the rate at which moisture leaves the slice As the moisture escapes it tends to puff the potato slices, resulting in an uneven, more textured appearance with small air pockets under the surface of the chip This imparts a lightness and crisper, crunchier quality to the chip.
In the apparatus, the sluice is provided upstream of the conventional fryer and downstream from a conventional potato slicer. The conventional fryer is typically associated with a heat exchanger which receives oil from the downstream end of the fryer, reheats it to a desired temperature and recirculates the heated oil back to the fryer. With provision of the sluice, only a portion of the oil from the downstream end of the fryer is routed to the heat exchanger.
The remaining portion is diverted to the sluice, with appropriate control to ensure that the oil introduced into the sluice is in the desired range of temperatures for caramelizing the starch envelope on the raw potato slices. Oil level in the sluice and the degree of precooking in the sluice are controlled through the use of variable speed paddle wheels located within the sluice.
The precooking method and apparatus of the above cross-referenced application has performed satisfactorily in producing on a continuous, high volume basis potato chips having an appearance, texture and flavor found heretofore in chips prepared on a batch basis. However, after an initial period of experience with the above-described precooking method and apparatus it has been realized that further improvements are needed to enhance the overall performance thereof and quality of the food product.